The present invention relates to a counter apparatus, which is best suitable for counting the number of prints in, e.g., an electrophotographic copying machine, for counting and managing the number of image forming operations.
A mechanical counter as a combination of an electromagnetic counter and a cam is conventionally used as the apparatus of this type. Recently, an electronic counter which is controlled by a microcomputer is becoming popular. For example, Japanese Patent Disclosure No. 60-133465 has been proposed as the prior art. In this art, a RAM is used as electronic memory means to store a total number of copies. In an apparatus described in Japanese Patent Disclosure No. 59-61854, the number of times of use of each image forming unit is individually stored in a nonvolatile RAM. This memory means loses data when a power source is turned off, and requires a backup power source to protect data. In an apparatus described in Japanese Patent Disclosure No. 57-163276, the number of prints is individually stored in a counter circuit for each image forming unit, and this counter circuit also requires a backup power source. When such a backup power source, e.g., a battery, is used, the battery must be periodically replaced due to its limited life and a user often forgets to replace it, resulting in inconvenience. While the main power source is in an off state, access to a RAM as memory means must be inhibited. When the RAM is incorporated in a CPU, the CPU must be set in a standby state and only the RAM must be set in the sleep state while being backed up. Thus, a specific sequence is required for turning on and off the main power source. When the backup power source is used, a period of time for saving data in the RAM is necessary. More specifically, the voltage of the main power source is monitored and before the main power source is completely turned off, the processing for saving the data in the RAM must be performed. For this reason, the arrangement of the apparatus becomes complicated, and this results in a high manufacturing cost. In contrast to this, an EPROM which does not require an additional power source can be used. However, in this case, in order to erase storage data, ultraviolet rays must be radiated for about 5 minutes, which is inconvenient for a frequently used machine.